Hot gas cylinder-piston apparatus

ABSTRACT

An operating cylinder and a regenerator cylinder are located adjacent each other, each cylinder having a manifold extending therefrom; a group of staggered U-shaped heating tubes connect the manifolds, the manifolds being arranged in planes which partly overlap, the legs of the U-shaped tubes being connected to wall portions of the parallel manifolds which are adjacently located, and so placed that the bends of the U-shaped tubes are positioned in planes which are parallel to the planes which include the manifolds; preferably, the widths of the manifolds change as a function of distance from the associated respective cylinder, the change being proportional to the change in flow of gases through the remaining portion of the manifold after gases have been drawn off from the preceding portion of the manifold by U-shaped tubes located in the preceding portions, the manifolds preferably being mirror images of each other, and of streamlined configuration.

United States Patent 1 Aupor et al.

[ Mar. 5, 1974 HOT GAS CYLINDER-PISTON APPARATUS [73] Assignees: Maschinenfabrik Augsburg-Numberg Aktiengesellschaft (M.A.N.), Augsburg; Mortorenwerke Mannheim AG, Mannheim, both of, Germany [22] Filed: Dec. 22, 1972 [21] Appl. No.: 317,778

[30] Foreign Application Priority Data France 60/24 Switzerland 60/24 Primary ExaminerEdgar W. Geoghegan Assistant Examinerl-l. Burks, Sr. Attorney, Agent, or FirmFlynn & Frishauf [57] ABSTRACT An operating cylinder and a regenerator cylinder are located adjacent each other, each cylinder having a manifold extending therefrom; a group of staggered U-shaped heating tubes connect the manifolds, the manifolds being arranged in planes which partly overlap, the legs of the U-shaped tubes being connected to wall portions of the parallel manifolds which are adjacently located, and so placed that the bends of the U- shaped tubes are positioned in planes which are parallel to the planes which include the manifolds; preferably, the widths of the manifolds change as a function of distance from the associated respective cylinder, the change being proportional to the change in flow of gases through the remaining portion of the manifold after gases have been drawn off from the preceding portion of the manifold by U-shaped tubes located in the preceding portions, the manifolds preferably being mirror images of each other, and of streamlined configuration.

17 Claims, 3 Drawing Figures HOT GAS CYLHNDER-IPTSTON APPARATUS The present invention relates to a hot gas pistoncylinder engine, in which the cylinder units of the engine have a regenerator associated with and located adjacent thereto, the hot space of the cylinder being connected to the regenerator by means of a reheater which includes a plurality of U-shaped adjacently located tubes.

Hot gas cyliner-piston engines utilize arrangements in which hot gases are delivered from one point ofa cylinder to be reheated. The reheating system may include a network formed of tubes, located in a row adjacent each other and placed such that the major plane of the tube network is perpendicular to the plane including the central axis of the cylinders and the regenerator.

It has been found that the links of the flow path of the heated gaseous medium used in cylinder-piston engines of the hot air type, which extends between the cylinder and the regenerator should be approximately of the same length and flow capacity, so that the working fluid which passes through central reheating tubes does not pass over a shorter path than working fluid which passes through the outer reheating tubes. If more fluid flows through some tubes than others, then the heat transfer which is effected through the tubes in the reheater will be different for different tubes, thus resulting in differential heat transmission and heat removal by the working fluid from the various heating tubes, and thus differential heating of the walls of the heating tubes themselves. If the walls of the heating tubes are not uniformly loaded, then those walls from which heat is not removed as much as design called for may be heated to an excessive temperature, resulting in burn out of those heating tubes.

It is an object of the present invention to provide a reheating system for hot gas cylinder-piston engines in which the flow paths and capacity between the cylinders and adjacently located regenerators are approximately equal for any one reheated tube, so that the flow of gases through the reheated tubes will provide for optimum heat transfer and substantially uniform flow of the gaseous medium therethrough, thus providing for approximately uniform heat loading on the various tubes themselves.

SUBJECT MATTER OF THE PRESENT INVENTION Briefly, the cylinders of the engine are each connected to manifolds located adjacent each other, the manifolds being interconnected by the legs of U-shaped tubes. The manifolds are arranged in parallel, partly overlapping planes, and the legs of the U-shaped tubes are connected to all portions of the parallel manifolds such that they are adjacently located, the bends of the U-shaped tubes being placed in a plane which is parallel to the planes which include the manifolds. In accordance with the preferred embodiment, the width of the manifolds decreases continuously from the origin of the manifolds adjacent the cylinder heads and as they extend from their respective cylinder head towards the other, the change in width of the manifold, as a function of distance from the associated respective cylinder being proportional to the change in the flow of the gases through the remaining portion of the manifold after gases have been drawn off from the preceding portion of the manifold by the U-shaped tubes located thereon.

The arrangement of the manifolds, as well as of the reheater tubes permits even loading, that is, substantially even heat transfer relationships at the respective heat exchange tubes, and approximately uniform flow resistance by the sum of the connected manifolds to the heater tubes, so that the flow through the heater tubes, individually, will also be effectively uniform. Thus, the temperature of the heater tubes can be maintained at the limit of the loading which the material can stand, thus permitting high efficiency of heat transfer. The heat flow, or flux can be increased, thus committing a decrease in the number and size of the reheater tubes. Since each reheater tube can be of the same size, subjected to approximately the same temperature ranges and pressures, the reheater tubes can all be made to be interchangeable, and reheater tubes made of different materials, or of different constructions in any one unit can be avoided.

It has previously been proposed (see U.S. Pat. No. 2,616,249) to provide reheater tubes located in the ring about the cylinder, the regenerator being likewise located in the ring about the cylinder, so that the path of flow of fluid between cylinder and regenerator tubes is approximately even or uniform. This arrangement, namely the ring-shaped location of the reheater tubes has the disadvantage that the reheater unit, normally including a burner, must be shielded from the cylinder by means of a heat shield, which is subject to very high temperature and thus has only a short life. Additionally, space limitations severely restrict the number of heater tubes which can be used, since the length of the circumference of the cylinder forms an upper and lower limit of the reheater, so that the reheater unit, supplying heat to the tubes, cannot be designed for optimum heat transfer efficiency. Additionally, the arrangement of the reheater tubes in a circular, closed ring has the disadvantage of requiring a good deal of space adjacent to or on top of the cylinder since the burner must be located in alignment with the reheater tubes themselves. Locating the reheater tubes, however, in accordance with the present invention in a plane such that the bends of U-shaped tubes are in a plane parallel to a plane which includes the manifolds permits space-saving construction, uniform loading on the tubes and efficient heat transfer.

The manifolds themselves preferably have rectangular cross-section, additionally contributing to a spacesaving arrangement. The parts themselves can be easily manufactured and the junctions, for example soldered, or brazed can be readily made since the junction locations will fall at easily accessible positions, and the number of junctions themselves is reduced to a minimum.

The manifolds can be made of substantial widths in those regions where the reheater tubes are connected thereto, thus permitting locating a large number of reheater tubes, adjacent each other and in parallel planes, on the manifolds. Overlapping arrangement of the manifolds in which the wider portion of a manifold reaches around, or next to the narrower portion of the adjacently located manifolds results in a structure which is of smooth outline, is economical in use of space and provides for short idle flow paths having a particularly low flow resistance and good flow distribution of the gaseous medium.

The side walls facing away from each other of the manifolds can be arranged in various ways; for example, if they are located perpendicularly to the longitudinal axes of the cylinders and of the regenerator, then a plurality of manifolds can be located adjacent each other without any loss of unusable space. The flow paths can be made of equal lengths and the entire unit can be shaped to provide a pleasing, smooth appearance.

The regions of the manifolds to which the reheater tubes are connected may be made, in accordance with afeature of the invention, to be of equal widths. The maximum width of overlap of the manifolds may then be approximately equal to the maximum extent of a cylinder-regenerator assembly or unit, resulting in a uniform, staggered row of reheater tubes when a plurality of cylinder-regenerator units are combined into an engine assembly. The number of burner units to heat the gases in the tubes thus need not be matched to any particular number of cylinders, but can be matched to the number of tubes present, and the burner units themselves can be so located that the heat from the burners can penetrate through the rows of reheater tubes without substantial change in direction of the flame or combustion gas path.

The covered surfaces of the manifolds and the legs of the U-shaped reheater tubes may be placed to be in a parallel plane. If so located, the connections or junctions of the reheater tubes to the manifolds can be easily placed. This construction permits use of reheater tubes having legs of equal length, thus facilitating manufactu re and assembly of the unit. The manifolds themselves, extending from their respective cylinders, may be mirror images of each other.

The invention will be described by way of example with reference to the accompanying drawings, wherein:

FIG. 1 is a fragmentary perspective, highly schematic view of a hot gas cylinderpiston engine complete with reheater tubes, with the burner unit omitted for clarity;

FIG. 2 is a perspective view of another embodi-ment of such an engine; and

FIG. 3 is a perspective view of yet another embodiment.

The hot space of a hot gas piston engine is illustrated at 1; it is connected to a regenerator 2 which is cylindrical and, in height and diameter, has roughly the same dimensions as cylinder 1. Cylinder 1 is closed off by means of a cylinder head 3; regenerator 2 is closed by means of a regenerator head 4. A manifold 5 is connected to cylinder head 3, located thereon at the outside and slightly off center; a similar manifold, forming a mirror image is connected to regenerator head or cover 4. Manifold 5 has one cover surface 6, and parallel thereto another cover surface (not visible in the drawing), the cover surface 6 (and the one parallel thereto) being located in a plane parallel to a plane which includes the central axis AA of cylinder 1 as well as of regenerator 2. This plane may provide a common limit for the manifold 5 as well as for the manifold 8 connected to the regenerator cover 4. Manifold 8 has one end surface 9, and a similar end surface, not visible in the drawing, parallel to the surface 6. Manifold 5, connected to the cylinder 1, is formed in its wall 11, opposite to the cylinder 1, with connections or junctions 12 for one leg of a row of U-shaped heater tubes 13.

The legs of the heater tubes 13, all placed in a row adjacent each other, form a tube assembly, or network located in planes parallel to the planes of .the side surfaces 6, 9 of the manifolds, the legs themselves being interconnected by means of U-shaped bends 14. The center of the bend 15 of the bends 14 is located in a plane defined by the axes AA, and further are located on a single line BB.' The second row of legs of the tubes 13 is connected to junctions or connections 16 which are formed in a wall 17 opposite wall 11 on the manifold 8 connected to the regenerator 2. The two manifolds 5 and 8, together with the tubes 13 form one structural unit or assembly having a length which corresponds approximately to the distance or space taken up by the widths of the cylinder and regenerator units together. Side wall 18 on manifold 5 and side wall 19 on manifold 8 (opposite side wall 18 on manifold 5) are parallel to each other. They merge smoothly and without a break in the outer surface of cylinder 1 and regenerator 2, respectively. The region or zone 21 of manifold 5, overlapping the gap 20 between cylinder 1 and regenerator is shaped to form a smooth curve, corresponding to the flow diameter of the manifold, as defined by a closing surface 22. The walls 18 and 22 interconnect the vertically extending surface 6, and its opposite (unnumbered) of the manifold 5. The width h of the manifold 5 is constant, or uniform over the entire length or surface thereof. Uniform flow diameter may, however, be additionally obtained by bulging or bowing the various respective covering surfaces.

Manifold 8 is a mirror image of manifold 5 and is formed with a region or zone 23 overlapping the gap 20 between cylinder 1 and regenerator 2. The overlap of the manifolds, one next to the other, permits arranging the manifolds with substantial length, without requiring any additional space for the manifolds beyond the maximum dimension between the cylinders and regenerator, and permits locating a large number of tubes 13 on the manifolds.

Operation: Working fluid expelied from the hot region within cylinder 1 flows into manifold S to the connections 12 in wall 11, then through the reheater tubes 13 in manifold 8, and then into regenerator 2. The lengths of the paths of fluid flow between the connections 12 in wall 11 of manifold 5 and the connection 16 in wall 17 of manifold 8, and, respectively, the cylinder or regenerator 1, or 2, are of different dimension. The lengths of the paths in the zones 21, 23 increases as the specific location on one of the zones 21, 23 recedes from the cylinder, or regenerator respectively. Since, however, a connection of a tube 13 from a projecting portion of one manifold always connects to a portion on the other manifold which is close to the other manifold at its connection to the respective cylinder, or regenerator, the overall length of path from the cylinder through the manifold, a tube 13 and then to the regenerator 2 will be uniform regardless of which reheater tube is selected to make the connection. Likewise, by shaping the manifolds to be of decreasing volume as they recede from the respective cylinder or piston (see FIG. 1) provides for uniform flow resistance of gases between the respective cylinder 1 or regenerator 2 and any selected tube 13.

As an example, a portion of the gas passing through the manifold 5 has to pass over a comparatively long path until it reaches the farthest removed connection point in zone 21 of manifold 5. The length of the path which this particular portion of gas has to pass through in manifold 8, however, is very short. On the other hand, gases which directly pass to the nearest connection adjacent side wall 18, need only traverse a short path; yet, the length of the path in region 23 of manifold 8 will be substantial. Comparing the lengths of the paths which any one partial mass of gas has to traverse in order to pass from cylinder 1 to the regenerator 2 will readily show that this length is substantially uniform, and, in view of the shaping of the manifolds, that the flow resistance to the movement of gas is also substantially uniform.

Embodiment of FIG. 2: The manifold 25 connected to cylinder 24 and the manifold 27 connected to regenerator 26 are tipped 90 with respect to the central plane which includes cylinder 24 and regenerator 26.

Other angular relationships may likewise be selected. The overlapping, cantilevered region 28 of manifold 27, located beneath manifold 25 reaches around cylinder 24 and extends the width of manifold 27 in the region opposite to wall 29, that is in the region opposite to the regenerator, so that it effectively extends the width of the cylinder-regenerator unit. The width of the manifold 25 likewise decreases as it extends aways from the cylinder 24. Wall 29 is parallel to wall 30 and offset with respect thereto. Overlap of the manifolds 25, 27 thus terminates at wall 30. The tube connections for the heater tubes 34 are located in the cover plate 31 of manifold 25 adjacent wall 30 as well as in a projecting portion 32 of the cover surface 33 extending from the manifold 27. The legs of the U-shaped heater tubes are, preferably as shown, perpendicular to the cover surfaces 31, 33 respectively and located in a plane defined by the axes C-C. The heater tubes are particularly uniformly loaded by heating fluid, for example flames and combustion gases, by offsetting the heating tubes in one row by half the width of their distance with respect to the heating tubes of another row. The differences in height between the two cover surfaces 31, 33 can readily be compensated by making the legs of heating tube 34 of different lengths. The heating tubes 34 end with their shorter legs in the upper manifold 25 and end with their longer legs in the lower man ifold 27.

The cover surfaces of the manifold 25, 27 respectively are formed with stiffening ribs 35. These stiffening ribs 35 are preferably uniform and integral with the cover surfaces, for example cast as one cover plate; they may also be added later and secured thereto by riveting, brazing, welding or the like, in order to increase the stiffness and strength of the manifolds themselves.

Embodiment of FIG. 3: The manifolds, as illustrated in FIG. 3 are similar to those in FIG. 2; manifold 37 is connected to cylinder 36, located adjacent the regenerator 38 having a manifold 39, the two manifolds being located at right angle with respect to the longitudinal axes DD of cylinder 36 and regenerator 38. The manifolds are located above each other. The connection points of the manifold 37 are formed with an end wall 40 located at the other side of cylinder 36; manifold 39 has an end wall 41 located at the side opposite, or away from regenerator 38. Walls 40, 41 are parallel to each other and located in a plane which is parallel to a plane perpendicular to the central axes DD of the cylinders 36, 38. The connection points for a row of U-shaped tubes 42 are located in the end wall 40 of manifold 37;

similar connection points are located in the end wall immediately there beneath of manifold 39. The tubes 42 are U-shaped having a pair of legs which are paral lel, and perpendicular to the plane defined by the central axes DD of cylinders 36, 38.

Manifolds 37, 39 are shaped to converge, or decrease in diameter; in addition, the interior surfaces of the manifolds are formed with vanes or guide elements 43, secured to, or integral with the cover surfaces of the manifold 37, 39. These guide vanes 43 or other guide elements can be Welded, or may be formed as thin sheet metal elements connected with the guide surfaces, or may be cast integrally with the cover surfaces as projecting ribs. If the cover plates are made by casting, the manifolds, and the adjacent regions of the cylinder or the regenerator, respectively, can be cast as integral units thus eliminating soldering, or brazing of the junctions of various structural elements.

Various changes and modifications may be made within the scope of the inventive concept and features described with reference to any one of the figures of the drawings can be applied mutatis mutandis with respect to another embodiment. The manifolds need not be arranged at any particular angle with respect to the planes included by the cylinder and regenerator, re-

spectively, but other planes are equally suitable. For example, the arrangement may be similar to that of V- arranged internal combustion engines.

Locating interiorally placed guide vanes similar to guide vanes 43 (FIG. 3) enhances uniformity of distribution of gas flow to the U-shaped tubes and simultaneously provides for stiffening of the manifold ele' ments. The U-shaped tubes may be formed, at least internally, to have streamlined configuration so that losses due to flow resistance of the working medium are held at a minimum and pockets of stationary or stagnant gas are avoided. The end corners of the manifolds themselves can be rounded. The manifolds themselves can be structurally interconnected to further increase the strength of the entire assembly and prevent undesired bulging under internal pressures.

Stiffening ribs on the outer surface of the manifolds (see FIG. 2: ribs 35) further increase the strength of the manifold units themselves. The wall thickness, and thus the temperature drop in the wall itself can be reduced, simultaneously providing for uniformity of expan-sion on the heating of the material of which the walls are made, over the entire wall thickness, and thus decreasing mechanical loading due to heat stress.

The apparatus of the present application is particularly suitable for use with hot gas, multicylinder piston engines of the type disclosed and claimed, for example, in copending application Ser. No. 315,930, filed 12/18/72.

We claim:

1. In a hot gas cylinderpiston apparatus having an operating cylinder (1) and a regenerator cylinder (2) located adjacent the operating cylinder, manifolds (5, 8; 25, 27; 37, 39), each connected to a respective cylinder,

and a group of staggered U-shaped heating tubes (13;

34; 42), the legs of the U-shaped tubes interconnecting said manifolds the improvement wherein the manifolds are arranged in parallel, partly overlapping planes, the legs of the U-shaped tubes being connected to the wall portions of said parallel manifolds which are adjacently located and the bends v of the U-shaped tubes being located in a plane which is parallel to the planes which include the manifolds.

2. Apparatus according to claim 1 wherein the manifolds have approximately rectangular cross section of approximately constant width (h).

3. Apparatus according to claim 1 wherein the depth of the manifolds decreases continuously as respective manifolds extend from, or project away from the respective cylinder to which it is connected.

4. Apparatus according to claim 3 wherein the change in depth of the manifold, as a function of distance from its associated respective cylinder is propor' tional to the change in flow of gases through the remaining portion of the manifold after gases have been drawn off from the preceding portion of the manifold by the U-shaped tubes located on and connected to said preceding portions.

5. Apparatus according to claim 3 wherein the depth of the manifold extending from the operating cylinder and towards the regenerating cylinder decreases continuously, and the depth of the manifold extending to the regenerating cylinder and from the adjacent operating cylinder continuously increases, the rate of change of depth of said manifold, with respect to distance from the respective cylinder being matched to the flow of gases, at any distance from the respective cylinder, through the manifold, and the total cross sectional area of the remaining U-shaped tubes along the length of the manifold.

6. Apparatus according to claim 5 wherein the respective manifolds are mirror images of each other.

7. Apparatus according to claim 1 wherein opposite sides (18,19) of the manifolds extend in planes perpendicular to the plane which includes said manifolds and the cylinder.

8. Apparatus according to claim 1 wherein the wall portions of the manifolds to which the U-shaped tubes are connected are of constant width.

9. Apparatus according to claim 1 wherein the depth of the manifold in the region of connection to the respective cylinder is approximately equal to the width of the respective cylinder.

10. Apparatus according to claim 1 wherein the U- shaped tubes are located in parallel planes and the end covers of the manifold (5, 8; 37, 39) extend in planes parallel to said planes. I

11. Apparatus according to claim 1 wherein the U- shaped tubes are located in parallel planes and wherein (FIG. 2) the manifolds (25, 27) have cover plates (31, 33) which are located in planes inclined with respect to said parallel planes.

12. Apparatus according to claim 11 wherein the angle of inclination is 13. Apparatus according to claim 1 wherein the manifolds (5, 8) have cover plates (6, 9);

said cylinders have central axes located in a plane;

and said cover plates are located in a plane parallel to said cylinder plane.

14. Apparatus according to claim 13 wherein the manifolds (5, 8) have cover plates;

' the cylinders have axes located in a cylinder plane;

and said cover plates are located in a plane inclined with respect to said cylinder plane.

15. Apparatus according to claim 1 further comprising guide vanes (43) extending in the manifold from the respective cylinder towards the connection of said U-shaped tubes.

16. Apparatus according to claim 15 wherein the guide vanes are formed as stiffening ribs and secured interiorally of said manifold.

17. Apparatus according to claim 1 further comprising outer stiffening ribs (FIG. 2: 35) secured to the outer surfaces of at least some of the portions of the manifolds. 

1. In a hot gas cylinder-piston apparatus having an operating cylinder (1) and a regenerator cylinder (2) located adjacent the operating cylinder, manifolds (5, 8; 25, 27; 37, 39), each connected to a respective cylinder, and a group of staggered U-shaped heating tubes (13; 34; 42), the legs of the U-shaped tubes inter-connecting said manifolds the improvement wherein the manifolds are arranged in parallel, partly overlapping planes, the legs of the U-shaped tubes being connected to the wall portions of said parallel manifolds which are adjacently located and the bends of the U-shaped tubes being located in a plane which is parallel to the planes which include the manifolds.
 2. Apparatus according to claim 1 wherein the manifolds have approximately rectangular cross section of approximately constant width (h).
 3. Apparatus according to claim 1 wherein the depth of the manifolds decreases continuously as respective manifolds extend from, or project away from the respective cylinder to which it is connected.
 4. Apparatus according to claim 3 wherein the change in depth of the manifold, as a function of distance from its associated respective cylinder is proportional to the change in flow of gases through the remaining portion of the manifold after gases have been drawn off from the preceding portion of the manifold by the U-shaped tubes located on and connected to said preceding portions.
 5. Apparatus according to claim 3 wherein the depth of the manifold extending from the operating cylinder and towards the regenerating cylinder decreases continuously, and the depth of the manifold extending to the regenerating cylinder and from the adjacent operating cylinder continuously increases, the rate of change of depth of said manifold, with respect to distance from the respective cylinder being matched to the flow of gases, at any distance from the respective cylinder, through the manifold, and the total cross sectional area of the remaining U-shaped tubes along the length of the manifold.
 6. Apparatus according to claim 5 wherein the respective manifolds are mirror images of each other.
 7. Apparatus according to claim 1 wherein opposite sides (18, 19) of the manifolds extenD in planes perpendicular to the plane which includes said manifolds and the cylinder.
 8. Apparatus according to claim 1 wherein the wall portions of the manifolds to which the U-shaped tubes are connected are of constant width.
 9. Apparatus according to claim 1 wherein the depth of the manifold in the region of connection to the respective cylinder is approximately equal to the width of the respective cylinder.
 10. Apparatus according to claim 1 wherein the U-shaped tubes are located in parallel planes and the end covers of the manifold (5, 8; 37, 39) extend in planes parallel to said planes.
 11. Apparatus according to claim 1 wherein the U-shaped tubes are located in parallel planes and wherein (FIG. 2) the manifolds (25, 27) have cover plates (31, 33) which are located in planes inclined with respect to said parallel planes.
 12. Apparatus according to claim 11 wherein the angle of inclination is 90*.
 13. Apparatus according to claim 1 wherein the manifolds (5, 8) have cover plates (6, 9); said cylinders have central axes located in a plane; and said cover plates are located in a plane parallel to said cylinder plane.
 14. Apparatus according to claim 13 wherein the manifolds (5, 8) have cover plates; the cylinders have axes located in a cylinder plane; and said cover plates are located in a plane inclined with respect to said cylinder plane.
 15. Apparatus according to claim 1 further comprising guide vanes (43) extending in the manifold from the respective cylinder towards the connection of said U-shaped tubes.
 16. Apparatus according to claim 15 wherein the guide vanes are formed as stiffening ribs and secured interiorally of said manifold.
 17. Apparatus according to claim 1 further comprising outer stiffening ribs (FIG. 2: 35) secured to the outer surfaces of at least some of the portions of the manifolds. 